1. Filed of the Invention
The present invention relates to a charging device and an image forming apparatus provided with the charging device, and more particularly to a charging device for charging an image bearing member and an image forming apparatus provided with the charging device.
2. Description of Related Art
An example of conventional charging devices is a corona charging device as disclosed by Japanese Patent Laid-Open Publication No. 2002-268342 (Reference 1). In the corona charging device, a corona wire is used. A high-voltage source is connected to the corona wire, and thereby, a discharge from the corona wire occurs.
Regarding such a corona charging device, as the discharge occurs again and again, silicon oxide and other substances adhere to the corona wire, and corona products, which are called as needles, are formed on the corona wire. Due to the corona products, the discharge from the corona wire becomes uneven, thereby causing a fault in charging. This is a cause of image noise.
In order to solve this problem, the corona charging device disclosed by Reference 1 has a cleaning assembly including a cylindrical grinding stone made of aluminum oxide. By a slide of the cylindrical grinding stone on the corona wire, the corona products deposited on the corona wire are removed.
In recent years, charging devices of a type that has a sheet electrode with aligned triangular pins are developed for practical use. This type of charging devices having a sheet electrode has the advantage over the charging device disclosed by Reference 1 of generating less ozone. However, the type of charging devices having a sheet electrode has the same problem as the charging device disclosed by Reference 1 in that corona products are generated. Therefore, also in this type of charging devices, it is necessary to clean the sheet electrode regularly.
The type of charging devices having a sheet electrode has also a problem that the pins are fragile. More specifically, an exemplary way of cleaning the sheet electrode is touching a grinding stone made of aluminum oxide as disclosed by Reference 1 to main surfaces of the sheet electrode; however, because the tips of the pins of the sheet electrode are sharp, the pins are relatively fragile. In carrying out this way of cleaning, therefore, the tips of the pins of the sheet electrode may be bent and/or cracked at a touch of the grinding stone. Then, the bent/cracked tips of the pins of the sheet electrode will cause a poor discharge, which results in degradation of picture quality.